Study on the effects and mechanism of temperature on the thermal decomposition characteristics of C4F7N/CO2/O2 mixed gas

To address environmental concerns arising from the potent greenhouse effect of SF6, C4F7N/CO2/O2 mixed gases have garnered significant attention as highly promising eco-friendly insulating media. This study employs ReaxFF molecular dynamics (ReaxFF-MD) to systematically investigate the thermal decomposition characteristics and reaction mechanisms of C4F7N/CO2/O2 mixtures across varying temperatures (2000–3000 K) and C4F7N volume fractions (4%–16%). Simulation results indicate that the decomposition behavior of C4F7N exhibits significant temperature dependence: decomposition proceeds slowly at 2000–2200 K, with residuals remaining after 500 ps; decomposition approaches completion at 2400 K; and the decomposition rate increases sharply above 2600 K, achieving complete decomposition within 300 ps. The primary decomposition products of the mixed gas include CF3, CF2, F, CF4, C2F6, C3F8, CF3CN, CO, CN, COF2, and C2N2. At low temperatures, stable fluorocarbon compounds and nitriles dominate, while at high temperatures, free radicals and small-molecule products become predominant. The C4F7N ratio primarily affects decomposition rate without significantly influencing the final decomposition extent. Mechanistic analysis indicates the decomposition follows an “O atom initiation–intermediate cleavage–radical recombination/oxidation” pathway, where temperature determines reaction pathways and product distribution by regulating the bond-breaking sequence (C–N < C–C < C–F). This study clarifies the regulatory mechanism of temperature on bond-breaking priority and the constraining effect of element conservation on product distribution. It provides theoretical support for optimizing environmentally friendly gas ratios and suppressing harmful decomposition products, thereby advancing the engineering application of SF6 replacement technologies and contributing to achieving dual carbon goals.